assume cs:code, ds:data, ss:stack

stack segment
    dw 0, 0, 0, 0, 0, 0, 0, 0
stack ends

data segment
    db 'ibm             '
    db 'dec             '
    db 'dos             '
    db 'vax             '
data ends

code segment
start:
    mov ax, data
    mov ds, ax
    mov bx, 0

    mov ax, stack
    mov ss, ax
    mov sp, 8

    mov cx, 4

lines:
    mov si, 0
    push cx ; mov dx, cx
    mov cx, 3

    chars:
        mov al, [bx][si]
        and al, 11011111b
        mov [bx][si], al

        inc si
        loop chars
        
    pop cx ; mov cx, dx
    add bx, 16
    loop lines

    mov ax, 4c00h
    int 21h
code ends

end start